Influence of Soil Reaction on Soil Acidity Parameters, and Fractions of Organic Matter, Nitrogen, Phosphorus and Potassium in Lateritic Soils of Konkan

An investigation was carried out on the influence of soil reaction on soil acidity parameters, and fractions of organic matter and NPK in the lateritic soils of Konkan region. Fifty-three surface soil samples from 0 to 22 cm depth were collected from various villages of the region and were classified into four different groups based on their pH values, viz., very strongly, strongly, moderately and slightly acidic. All the forms of acidity, viz., total, exchangeable and pH-dependent, showed decreasing trend from the very strongly to the slightly acidic soil groups. Lime requirement by the SMP buffer method also decreased with increase in pH. The mean value of organic carbon content, humic acids and fulvic acids were 16.00, 7.18 and 6.02 g kg⁻¹, respectively in the very strongly acidic soil group and 7.00, 3.49 and 2.96 g kg⁻¹, respectively in the slightly acidic soil group. The data on all the fractions of nitrogen showed continuous decline with increase in pH. In case of P fractions, Fe-P and Al-P exhibited reduction in slightly acidic soils than in very strongly acidic soils, whereas all other P fractions were increased with rise in pH. None of the K fractions showed any definite trend with changes in pH. All the forms of acidity and lime requirement had very highly significant negative correlation with soil pH. The NH₄-N, NO₃-N and amino acid N contributed towards significant variation in soil pH, while among P fractions Al-P, saloid-P and occluded-P contributed towards significant variation in changes in soil reaction.